1. Field of the Invention
The present invention relates to a heating floor or sole for heating an object, such as a substrate, which is preferably thin and placed on its surface, as well as to a chemical treatment reactor having such a sole.
2. Discussion of the Background
Chemical treatment reactors more particularly make it possible to produce deposits of materials, e.g. by the procedure known as chemical vapour deposition or CVD, on a substrate. Said substrate is generally a silicon wafer used in the manufacture of electronic components. This type of chemical treatment requires the substrate to be heated to between 20.degree. and 1000.degree. C.
Chemical treatment reactors are able to heat the substrate either indirectly by radiation emitted by a light source such as tungsten halogen lamps (cf. in particular the reactor of the Spectrum Company), or directly by contact between said substrate and a heating plate (cf. in particular the reactor of the Varian Company). In the case where the substrate is placed on a heating plate, the temperature distribution at the substrate directly corresponds to the temperature distribution on the plate.
However, in reactors, said substrate is sometimes kept in contact with the plate by a peripheral clamping ring, which exerts a pressure on the periphery of said substrate. As said ring is generally a good heat conductor, locally there is frequently a temperature drop in the substrate.
Moreover, in the prior art plates, the metal bed or base plate thereof only contains a single heating resistor positioned in accordance with a particular spatial distribution, which is adapted to its use. As this heating resistor is traversed by a single current, the only possible temperature variations on the surface of the plate are due to surface distribution differences of the heating resistor in the bed plate. It is therefore difficult for steric dimensional reasons to overheat a precise zone in order to make up for a local temperature drop.
U.S. Pat. No. 3,134,006 discloses a temperature checking system for a heating element having sensors and control loops of the master and slave type. EP-A-165 114 discloses a heat regulating device for a hot runner mould. However, the teachings of these documents are not applicable to a heating plate.
It would therefore be desirable to have a heating plate whose surface temperature can be more accurately adjusted and whereof the heat quantity supplied by the two surface zones of the plate can differ even if said zones are small and contiguous.